So far, for example, Patent Document 1 discloses a combustion diagnosis method of an internal combustion engine that allows the difference between pre-ignition and abnormality of an in-cylinder pressure sensor to be distinctly discerned and determined by use of the in-cylinder pressure sensor. The conventional combustion diagnosis method determines that pre-ignition has occurred when the standard deviation of a change in an in-cylinder pressure at a predetermined crank angle before ignition is equal to or larger than a threshold value of the standard deviation and a load factor in-cylinder pressure difference that is obtained by dividing a pressure difference of the in-cylinder pressure between a reference crank angle and the top dead center by a load factor on the driven side is equal to or larger than a threshold value of the load factor in-cylinder pressure difference.
Including the above described document, the applicant is aware of the following documents as related art of the present invention.